I'm currently using two-factor between my Mac and iPhone. And I also use it for my Google account. (Those are the two only ones at the moment.)
How I can protect access to my accounts if I don't have a mobile phone?
First, I'd like to understand if two-factor on a mobile phone is stronger than using a two-factor method that does not involve a mobile phone? If so, what particularly about a mobile phone makes it more secure? Is it because mobile phones have SIM cards, and no-one can get a SIM card without signing up with full name with a phone carrier, etc.?
What alternatives do I have for two-factor for Apple ID / Gmail that does not involve a mobile phone? (Preferably something that does not require obtaining a physical item or signing up for some paid service.) Can sending a token by encrypted email be used, for example?